Polymerase chain reaction cloning and expression of the rat granulocyte-macrophage colony-stimulating factor

We used reverse transcription-polymerase chain reaction (RT-PCR) to clone a rat complementary DNA that encoded the PVG rat granulocyte-macrophage colony-stimulating factor (GM-CSF). PCR products were cloned into a eukaryotic expression vector and transfected into the mouse myeloma cell line Sp2/0-Ag14. Cell culture supernatants of two of these transfectants supported proliferation of the growth factor-dependent cell line, DA-3, and promoted myeloid colony formation in rat and mouse bone marrow cell (BMC) cultures. The GM-CSF activity in these supernatants was neutralized by a polyclonal antibody to mouse GM-CSF. The cloning and expression of rat GM-CSF provides a valuable reagent for the study of the biology and clinical applications of the GM-CSFs.